I have been searching for a while now for a way to create more than the default, nether, and end worlds to play in.

Example: I want a PvP world, a no-grief world, a grief-allowed world, etc.
Is this possible by any way? I want all worlds to be active at the same time ie. players can be playing on all worlds at the same time.

I would also like to be able to make portals to the world ie. go in them and you warp to the world.

Is this possible by any way? Please don't post such complicated answers as I am not too much of an expert with Bukkit.

I've actually seen this on one server (and I rarely play Multiplayer) on Redstone Development Foundation. I KNOW there is a way to have multiple worlds. I just dont know how the hell it's done, but you got my confirmation :D
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user1337Feb 28 '13 at 17:16

An alternative to Multiverse is My Worlds. I've always found it to be more stable and less lagy. Currently doesn't support 1.5.* but only because BKCommonLib is being slack at updating. I would suggest using Multiverse until BKCommonLib updates and then switch.